Source : Webster's Revised Unabridged Dictionary (1913)

Enclosure \En*clo"sure\ (?; 135), n.
   Inclosure. See {Inclosure}.

   Note: The words enclose and enclosure are written
         indiscriminately enclose or inclose and enclosure or
         inclosure.

Source : WordNet®

enclosure
     n 1: artifact consisting of a space that has been enclosed for
          some purpose
     2: the act of enclosing something inside something else [syn: {enclosing},
         {envelopment}, {inclosure}]
     3: a naturally enclosed space [syn: {natural enclosure}]
     4: something (usually a supporting document) that is enclosed
        in an envelope with a covering letter [syn: {inclosure}]